1. Field
Embodiments of the present invention relate to a method and protocol for high-speed data channel direction control.
2. Description of the Related Art
Previously, sideband or auxiliary lanes (e.g., wire pairs, wherein one lane is a pair of differential wires) transported low-speed data on a bi-directional link.
An example is the MIPI DSI v1.1 display interface. This display interface permits one lane of four (e.g., lane 0 of lanes 0-3) to reverse direction from normally high-speed downstream into low-speed upstream. Accordingly, one high-speed lane may be “turned around,” or “reversed,” enabling the lane to switch from operating in high-speed downstream to operating in half-duplex, or low-speed, upstream. However, the MIPI DSI display interface is not capable of increasing downstream bandwidth, and is also not capable of providing data in the “reversed” upstream direction at high-speed.
For example, when the MIPI DSI display interface causes the data transmission along one of the lanes to switch directions, the link is turned off, and a character is sent to explain that the host, or transmitter (e.g., the device sending downstream data) is turning control over to the peripheral, or receiver, to thereby initiate the drivers of the receiver. This causes the high-speed downstream to power down, and the low-speed upstream to power up.
As video display resolution and frame rates increase (for example, the display resolution for televisions is expected to increase from 1920×1080 (2 Mpixels) to 7680×4320 (32 Mpixels) by 2016, while the display resolution for tablet computers is expected to increase from 1200×800 (1 Mpixels) to 2560×1600 (4 Mpixels) by 2014), lanes that carry pixel data to the corresponding display will need to have an increasing amount of bandwidth to carry an increasing amount of pixel data to allow the display to have operate with the increased resolution.
However, the data rates of the physical layer are generally not increasing at the same rate at which the data will need to be transmitted in accordance with increased display resolution. Accordingly, many display interfaces will compress the display stream data to compensate for a lack of available bandwidth on the physical layer, thereby reducing the amount of data that will be sent.
With respect to compression of the display stream, data compression can be lossless, which is ideal, or lossy, wherein some integrity of the image quality is lost during transmission. Certain types of data may be difficult to compress in a lossless manner. Further, lossy compression can result in visual artifacts that can be noticed by the user, thereby reducing the quality of images displayed.
Accordingly, by increasing link bandwidth, the amount of necessary compression can be reduced. Therefore, images transmitted across a link having increased bandwidth may be transmitted using a higher quality lossy compression, or may even be transmitted using lossless compression.